Techique for providing back bar and boss for slider

ABSTRACT

Salient embodiments comprise magnetic recording sliders whose record-confronting face is characterized by two or three rails wherein stiction forces are counter-acted by provision of a &#34;boss&#34; on one or several rails, or therebetween; and also characterized by provision of a &#34;back-bar&#34; and associated a purge channel; and methods for rendering such are also described.

This is a division of application Ser. No. 07/896,717 filed Jun. 10,1992, now U.S. Pat. No. 5,220,470, issued Jun. 15, 1993, which is adivision of U.S. Ser. No. 225,680, filed Jul. 29, 1988, now abandoned,which is a division of Ser. No. 836,364, filed Mar. 5, 1986, nowabandoned.

FIELD OF THE INVENTION

The present invention relates to magnetic head-slider assemblies, andmore particularly to air bearing slider assemblies used for noncontactrecording in magnetic disc files and the like.

PRIOR ART, INVENTION FEATURES

Workers are aware of prior art techniques to utilize magnetichead-slider assemblies. In such an air bearing slider assembly, magnetictransducers are affixed thereto for non-contact recording on a passingmagnetic disc. Workers know how to mount such magnetic head assemblies(having air bearing sliders) onto carriages--e.g., to be used inintegrated data modules for storage of information in a magnetic discfile.

Tremendous efforts are being made now to increase the density of storageon such magnetic discs--e.g., workers are trying to narrow disc-trackwidth, reducing the spacing between each track to increase the number oftracks per inch. Likewise, workers are trying to develop head assemblieswhich are capable of recording and reproducing information using minimaldisc area.

For instance, to improve recording density in disc drives- used ascomputer peripherals, it is believed vital to increase linear recordingdensity as well as the track density (so many more tracks per inch maybe recorded on a disc). It is also necessary to so record information asto be retrieved reliably, and as rapidly as possible, and to reduce thecost per byte. Thin film head technology is now successfully used tofabricate recording transducer elements. And, it is now accepted that anumber of transducers, accurately spaced, can be laid down on a singleslider body at little or no cost sacrifice.

Other workers have suggested placing one or more transducers at the"trailing edge" of the air bearing (rail). But this can be costly--e.g.,for the manual labor to install wirewound transducers "in line" with anair bearing surface.

This invention provides an improvement over conventional "low-mass"sliders .(i.e., "Winchester" or "self-load" types) , in the addition ofa "full back bar" on the slider. This "back bar", when added to a"self-load" slider (e.g., see FIGS. 5-8), does not upset performance,yet can allow one to increase the number of slider-heads independent ofthe number of rails. The "back bar" is characterized by anair-passage-slot (i.e., "purge channel") cut perpendicular to the airbearing surface and parallel to the "back bar". Such a "back bar" canprovide a "positive pressure distribution" able to reduce the"pitch-restoring moment"; thus, it can reduce "pitch angle". Such aback-bar is easy to fabricate, "and can provide a "cleaner" slidersurface that is closest to the disc (magnetic media).

And a like back-bar/purge channel combination can provide similarenhancement for a Winchester type slider (e.g., see FIGS. 1-4 for a moreconventional Winchester; also see U.S. Pat. No. 4,081,846 and art citedtherein).

"Comparison Model" (FIGS. 1-4)

FIGS. 1-4 schematically depict a "modified Winchester" type sliderassembly wherein "flying height" will be understood as controlled bymeans of a differential fluid release bypass aperture, and/or by varyingother parameters, such as the rail width. This model is intended forcomparison with the preferred embodiments (e.g., having mere reliefslots P, R rather than a "back bar" and "purge-channel").

Workers will recognize such a magnetic head-slider assembly 10 as likethose commonly used for flying a magnetic head on an air-bearing over adisc or like information-storing medium (see plane M--M of mediumpassage). Slider assembly 10 has a support body 11 (ceramic) with a topsurface (shown generally as a) and an opposed air-bearing surface, showngenerally as b. Surface b is to be "flown" above the disc surface (asshown diagrammatically by arrow) and in a predetermined direction. Thesupport body 11 has a leading edge c and a trailing edge d (takenrelative to travel of the media, as depicted by arrow). The fluidbearing surface b has a pair of parallel, planar fluid support rails f,g extending in a direction opposite to the predetermined direction ofmovement (shown by arrow). Each end of the support rails has a leadingedge which is canted slightly, away from the media plane M--M, to form aslight angle between the edge of each fluid support rail and the planedefined thereby.

Workers will appreciate that a flat fluid support surface h extendstransverse to the predetermined medium plane M--M; surface h will beunderstood as extending between, and substantially planar to, airbearing rails f and g, to define a trailing edge d relative to theleading edge c.

Also, there is a ramp. surface k extending from the flat air-bearing(fluid support) surface b, and between the spaced rails f, g. Rampsurface k is set at a preselected angle α and leads to a wedge-shapedcavity L having an opening located between the leading edges of rails f,g, respectively. The wedge-shaped cavity L is typically about 350 u"deep and has a closed end m located adjacent the flat air-bearingsurface h. There is one, or several, magnetic transducer(s) fixedlymounted at the trailing edge d of the body 11. Each magnetic transduceris positioned with its R/W gap adjacent to, and aligned with, the flatair-bearing surface d. Now, here, a pair of spaced parallel "reliefslots" P, R are formed through the trailing edge d of slider body 11.Slots P, R extend in a direction substantially parallel to the spacedparallel support rails f, g and communicate with ramp surface k.

Of course, one must guard against detritus clogging slots P, R or cavityL (e.g., this can lead to a catastrophic head crash). Now, some detritusbuild-up is virtually certain with such sliders. For instance, the bestfilters ["99.999%" type] correctly used with such equipment willcustomarily exclude all atmospheric contaminants larger than about 12u". This should eliminate most smoke particles (usually ˜250 u") . Butsmaller air-borne contaminants abound and can readily build-up inshallow cavity L (especially at its trailing edge) and/or in slots P, R[e.g., commonly: oil vapor from the disk drive bearings, particles fromthe media--also smog, atmospheric dust and fumes, rosin smoke,metallurgical dust and fumes, viruses, etc.]. Thus, the art needs abetter contaminant-free slider which avoids, or mitigates, such problems(e.g., better than the "slotted" model of FIGS. 1-4). This is a salientobjective of my invention.

Thus, as one feature hereof, an improved, more contaminant-free flyingslider is provided with a "back-bar" and associated transverseflush-cavity (purge channel) adapted to better accommodate multipleheads at the lowest point of slider's flying face (above disc), toreduce pitch angle, to better "flush" the slider (cf. more reliable wayof keeping "negative-pressure-orifice" clean), to facilitate fabricationof thin film heads (lower cost, yet high reliability due to accuracy ofmasking techniques), and to effect improved "purging" (at the R/W gap).

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantage present invention will beappreciated by workers as they become better understood by reference tothe following detailed description of the present preferred embodimentswhich should be considered in conjunction with the accompanyingdrawings, wherein like reference symbols denote like elements.

FIG. I depicts, in side schematic view, a "comparison model" as a"modified Winchester" type slider riding above a disc surface, thisslider being shown in perspective in FIG. 2, in plan view in FIG. 3 andend-view in FIG. 4;

FIGS. 5 and 6 depict, in like schematic view, a "self-loading" typeslider embodiment modified according to the invention, with a sideview-thereof in FIG. 7 and an end-view in FIG 8;

While FIGS. 9A and 9B indicate an idealized pressure-profile alongrespective axes of this embodiment, with FIGS. 10 and 11 indicatingrelated idealized relationships of head flying height and pitch angle(vs load); and FIGS. 22, 23 indicating flying height vs velocity, load,respectively;

FIG. 12 schematically indicates operational attitude (side view) of suchan embodiment, while FIG. 13 indicates the same without the invention;

FIGS. 14 and 15 plot flying height vs time over a 6 u" bump for two"purge channel" depths in such an embodiment;

FIG. 16 depicts, in schematic side view, a "back-bar attachment"embodiment;

FIG. 17 is a partial plan view of a modified embodiment;

FIGS. 18A, 18B, 18C are partial side views of modified purge-channelcross-sections;

FIGS. 19A, 19B are respective plan, side views of an embodiment likethat of FIG. 16;

FIGS. 20, 21 are respective plan, side views of yet another embodiment;

FIGS. 22, 23 are plots of slider flying height vs velocity, and vs load,respectively;

FIGS. 24A, 24B are plan and side views of a slider (e.g., per FIG. 9A)with both a back bar and a boss;

FIG. 25A is a "test plot" of disk surface roughness (acoustic emissionsensor output) across a given disk radius; while FIG. 25B is the sameplot after "burnishing" this disk surface with a "back-bar-furnished"slider; and

FIG. 1'A is a schematic elevation of a representative slider embodimentprovided with a boss means as shown parked on a magnetic recording disk,while FIG. 2' is a plan view, FIG. 3' a side view, and FIG. 4' anend-view of this slider;

FIGS. 1B, 1C' are respective plan and side views of a relatedembodiment;

FIG. 5' is a plan view of a related 3-boss embodiment;

FIG. 6' is a plan view of a related 2-rail embodiment;

FIGS. 7' and 8' are respective plan and side views of a related"medially-mounted" boss embodiment;

FIGS. 9'-11' are respective end, plan, and side views of a relatedpiezo-boss embodiment;

FIG. 12' is a plan view of an embodiment like that of FIG. 6' where thebosses are deformed by lapping or cold-worked; and

FIGS. 13' 14', 15' and 16' represent plots, for certain embodiments, of"particle count" vs. "stop-start test time".

DESCRIPTION OF PREFERRED EMBODIMENTS General description, background

FIGS. 5-8 schematically illustrate a "self-loading" type slider assembly20 constructed and modified according to principles of this invention.This, and other related techniques and means discussed for allembodiments, will generally be understood as constructed and operatingas presently known in the art, except where otherwise specified. And,except as otherwise specified, all materials, methods and devices andapparatus herein will be understood as implemented by known expedientsaccording to present-good practice.

More particularly, FIGS. 5-8 will be understood as schematicallydepicting such a slider 20 which is improved, according to theinvention, to include a prescribed "full back bar" 21 and associated"purge channel" 23 extending transverse to the direction of flight(arrow)--e.g., compare the "slotted" slider in FIGS. 1-4. Slider 20 willbe recognized by workers as otherwise conventional, comprising a ceramicbody 1 with a leading edge portion 20-L and a trailing edge portion20-TR, a pair of (positive-pressure) side-rails 20-R, 20-R' (includingprojecting ramped lead-tips 20-T, 20-T'), plus a very shallow interioraerodynamic cavity 20-C (or "negative-pressure channel") of prescribedprecise dimensions (usually, up to several hundred μ-in.).

It has been found that surprising effects may be produced by aprescribed extension of the slider length to accommodate a "back-bar" 21and intervening "purge channel" 23 of proper dimensions, designed toreduce the pressure to zero (atmosphere)--and yield such effects asflushing the dirt particles away from the transducer end.

In particular, this allows multiple transducer means to be locatedanywhere across the "back bar" (compared with conventional sliders as inFIG. 13). This "back-bar" extends the full width of the slider (trailingedge)--i.e., to be a "full back bar" (no advantage to less than fullwidth) and it may be of any suitable width (along direction of axis A)depending on pitch angle required (e.g., here, several mils width wasfound suitable).

The "purge channel" 23 is cut just upstream (forward) of the back-bar 21along the slider face 20-f. Channel 23 will be located (along axis A)such as to 1 terminate cavity L and to distribute positive and negative(dynamic) forces as understood by workers. Channel 23 will in someinstances be cut in two segments (e.g., as schematically suggested inFIG. 17, for fabrication convenience, etc.--a non-preferred casehowever; FIG. 17 to be read like FIG. 5). Channel 23 may becross-sectionally shaped in the rectangular mode of FIG. 7(square-corners; e.g., for fabrication convenience) of virtually anyother shape (e.g., see alternatives 23-A, 23-B, 23-C in FIGS. 18A, 18B,18C, respectively)

For instance, satisfactory operation has been observed with aself-loading slider like slider 20 (FIGS. 5-8) about 170 mils in lengthL (L_(c) =93 mils) by 40 mils in height h (h_(c) =25 mils), by 110 milsin width w (w_(c) =80 mils); with rails having a width w_(r) of about 15mils [ramp h_(p) about 0.175 mils in height h_(r) ; tips 20-T about 20mils in length, t_(e) --bar 20-L about 20 mils in length, f_(e) ] withinner "flying-cavity" 20-c about 500 micro-inch in depth d_(c) and 80mils in width w_(c).

For this slider, under relatively conventional "flying" conditions(e.g., disc surface-velocity about 1500 inch/sec), it is foundsatisfactory to make "back bar" 21 about 5 mils wide (w_(b)) and"square" in cross-section (cf. FIG. 7) with a purge channel 23 about 0mils wide (w_(p)) and about 4 mils deep (d_(p)) and "square-cut". Thisafforded a stable flying height of about 5-7 micro-inch (at trailingedge, along back-bar), and showed fine "self-flushing"characteristics--such that workers would likely be surprised.

Operation of Preferred Embodiment (see FIGS. 9-13)

FIG. 12 diagrammatically suggests how such a slider 20 is intended tofunction, as opposed to a like slider 30 lacking the "back-bar" and"purge channel" (both sliders assured to be flying above a disc at adesired attitude, for read write operations). The trailing corner 31-Tcof conventional (self-load) slider 30 in FIG. 13 will-be visalizedas-allowing relatively little air (compressed by slider flight) toescape, and will be seen as approaching so close ("trailing corner"31-Tc of flying-face 30-f at trailing-edge 31) to the passing discsurface (see plane M'--M') as to readily be occluded by debrisbuild-up--such as to "block" the desired, necessary purge of its"negative-pressure-channel" 30-c.

By comparison, when analogous embodiment 20 is provided with a back-bar21 and associated purge channel 23 (see FIG. 12) to purge its"negative-pressure-channel" 20-c of debris, air can readily and quicklyescape to atmosphere, so the slider 20 may purge itself of debris quiteeasily. [Note the relatively "massive" dimensions of purge-channel 23compared with the miniscule depth of n-p channel 20-c.] Such "purging"along such a relatively massive channel (cut transverse to the flyingdirection) is found different from (and superior to) the proposed designair escape configurations such as "parallel slots" (cf. FIGS. 1-4 and"slots" P, R). This proposed design is not as practical or economical,etc., as I would like.

Thus, this "full back-bar/transverse purge channel" design improvesoperational and other characteristics of the usual "self-load" slider,giving a massive air purge conduit across to the air bearing surface (tovery effectively flush cavity 20-c ) and parallel to the back-bar. The"positive pressure" and the "negative pressure" regions provide the "netload" across the air bearing surface (compare FIG. 9 with FIG. 5). Thepositive pressure surfaces (along axis B; cf. FIG. 9B) fully flank themedial negative pressure area (e.g., along axis A; cf. FIG. 9A). Theresultant (net, loading) force due to these pressures provides arelatively constant load over the slider bearing. Changes in air flow ordisc will have a negligible effect on this loading; hence, a more stableair bearing surface is realized.

The positive loads due to positive pressure distribution along the siderails and the "back-bar" control the "bearing stiffness" of the slider.The sum of these positive loads tends to increase the "net load",resulting in a higher air-bearing-stiffness (see FIGS. 9A, 9B forpressure profiles plotted along axis A, axis B of slider of FIG. 5--FIG.10 is a comparable plot of flying height vs load for like "self-load"back bar-equipped sliders, ZL FBB (Zero Load, Full Back Bar) with flyingcavities of different depths).

Workers will note that as cavity depth (cd), increases the flying height(fh) increases and becomes less linear vs load change--and tends toapproach the characteristics of a more conventional slider OW (ordinaryWinchester, no Back-Bar). Note: cd of such ZL FBB sliders determinesfh--something novel in the art--also, suction decreases as cd increases.Thus, a worker would likely prefer a MIN cd design (e.g., 100 u");however for ease and reliability of rendering such miniscule "cd cuts",we prefer a cd of about 300 u" (or slightly more).

The positive pressure distributed along the back-bar surface willincrease slider stiffness. This added stiffness will tend to improvecontrol of the slider and inhibit undesirable "roll" (e.g., about axisA, FIG. 5). The presence of such positive back-bar pressure also acts toreduce the "pitch restoring moment", and thus reduce "pitch angle" (seeFIG. 11 which pitch angle is plotted vs load for such a "zero load fullback bar" slider (ZLFBB) vs OW, as in FIG. 10) at various flying-cavitydepths).

Workers will be surprised to note that, unlike the ordinary slider, such"back bar sliders" are so relatively insensitive to changes in load(especially the smaller cd, at least for such minor load changes). Alike (surprisingly) insensitivity to disc-velocity is also observed.

This is seen in FIGS. 22, 231 which plot f lying height (fh) vs velocityand load respectively for a zero load full back bar sl (ZLFBB, assume300 u" cavity) vs an ordinary slider OW (no back bar), as with FIGS. 10,11 above mentioned. Surprisingly, it will be evident that the ZLFBB isconsiderably less sensitive to such disc velocity changes (FIG.22--despite carrying a small fraction of the load OW carries).Similarly, a pair of ZLFBB sliders Z₁, Z₂ (assume 300 u" cd; 22 milrail-width) exhibit relatively little sensitivity to (minor) load changeas compared with more conventional (no back bar) sliders OW₁, OW₂ ; evendespite varying velocities (about 1500 ips for Z₁, OW₂ ; about 2500 ipsfor Z₂, OW₂ ; about 2500 ips for Z₂, OW₁).

Operating with the Mentioned slider embodiment (cf. disc velocity of1508 in/sec; positive pressure rails 15 mil wide and 500μ-inch negativeair-pressure cavity), an escape passage 23 as in FIGS. 5-8 and 10×4 milsin cross section (for a flying height of 5 to 7 μ-inch under theback-bar) increased bearing stiffness (e.g., by about 10%), gave bettercontrol and less "roll", while reducing "pitch angle" (e.g., from 130u-radians to 90 u-radians).

Tests of Modified Embodiments (FIGS. 14, 15)

FIG. 14 is a plot of "flying height" (in u") vs time for a comparable(back-bar equipped) slider as it is made to traverse a miniscule bump 6u" high [here, the "flying-cavity" 20-c is only 200 u"; flying at 1508m/sec at a height of 6.8 u" and a load of negative 10 gm.]. FIG. 15 is alike plot under the same conditions [except cavity 20-c is 500 u"; loadof +1 gm; slider displaced from flying height of 8 u" by test force].Workers will agree that the setting time of 0.00038 in FIG. 14 and of0.0007 in FIG. 15 indicate fine stiffness.

Alt. Embodiment (FIGS. 20, 21)

FIGS. 20, 21 schematically illustrate another alternative slider SL-20(modeled after slider of FIGS. 6, 7--but with full-width ramp 200-T).Here, it was found that a certain pitch angle was too great to yieldgood flying (height) stiffness so increasing the width of back-bar 221(empirically, as workers will perceive) until pitch angle was properlydecreased cured this problem.

Modifying Winchester Slider (FIGS. 16, 19A, 19B)

A Winchester slider (e.g., like that shown in FIGS. 1-4) can also bemodified to simply append such a "back-bar" and associated "purgechannel", with the same sort of performance enhancement, cost-savings,etc., For instance, an "add-on" ""back-bar/purge channel" arrangement BBas schematically depicted in FIGS. 16 could be affixed at the trailingedge of a winchester slider like that in FIGS. 1-4 [here, assume theslider 11' in FIGS. 19A, 19B; FIG. 19A being a plan view like FIG. 3 orFIG. 6; and FIG. 19B a side view]; after cutting-off a trailing sectionof comparable length 16-L (FIG. 16).

More particularly, referencing to slider 11', an "extension" B--Bthereof is depicted in side-view in FIGS. 16, 19B, to be understood asadapted for attachment along the entire trailing-face of slider 11',with Lead-face 59 of attachment BB understood as joined to f ace d, the"trailing face"--see FIG. 2 also, with the "wall h" being cut-away toopen-up the exit from cavity L, between slots P, R [face 59 beingcongruent with face d except for a channel cut-out therealong at 51,channel 51 being cut-into bearing-face 53 of B--B, which will thusextend the bearing-face of slider 11' and eliminate wall h]. Thus,attachment BB will be understood as leaving slider 11' with the sameeffective-length, and providing a new trailing-face 55 (vs prior faced), along which transducers may be sited at will. The associated purgechannel 51 will be understood as cut-out along flying-surface e 53 ofthe attachment B--B (affording a better flying stability--e.g., atflying height of 35-45 u").

Of course, alternatively, the slider may be originally fashioned toinclude such a purge channel/back bar combination.

Moreover, it should be appreciated that, with such a "full back bar",one can better realize the cost-saving potential of associated thin filmbeads--no added hand labor for winding heads, etc. An array of thin filmheads can fill the entire back bar, with no limit on their number(except for size and economic limitations). And the associatedpurge-channel introduces an escape passage to better keep the"negative-air-pressure-exit" free of debris.

Thus, workers will note that use of such a "full back-bar" and"transverse purge channel" on a slider allows a great number of heads tobe disposed at lowest (flying) point of the slider, how it reduces pitchangle, how it minimizes the risk of debris blocking thenegative-pressure-orifice, how it makes it less costly to fabricate aslider with thin film heads (enhancing reliability due to theprecise-locating resulting from associated thin film maskingtechniques), and how it can afford a helpful "purging effect" at the R/Wgap.

"boss"

Workers in the art of magnetic disc recording for computer memory andrelated purposes are familiar with certain problems suffered by themagnetic head sliders used to present the transducer means to therotating disc. One problem is that of "stiction" (forces) developed whena slider is resting on the magnetic disc surface (e.g., on a lube filmthereon). Stiction forces can be undesirably large andcounter-productive, especially under the "sudden start" conditionsusually desired--e.g., overloading the disc-rotating motor--[they canlead to damage to the slider and/or to the disc surface].

Stiction can commonly induce a transfer of disc-material onto the sliderrails; at times causing a flying slider to crash into the disc andrender it useless. Such crashes become more and more likely as slidersare made to fly lower and lower [presently as little as about 20micro-inches above the disc, a flying height which obviously can lead todisastrous problems if just a few micro-inches of material is picked upon a slider rail]. It is an object of this invention to ameliorate suchproblems by providing anti-stiction boss means arranged to protrudebelow the surface of the slider.

Such stiction and related problems are exacerbated by the current trendtoward reducing "lube thickness". Conventionally now, a disc surface islubricated with a somewhat uniform coating of an industry-standardpolymer (e.g., by Brayco, Krytox, etc.) normally, at least 50-70 Å indepth--being depleted in use to about 11-20 Å, which approximates a meremonoatomic layer and thus is thought to be as thin as possible for sucha continuous film. A head/medium interface that requires no lubricationat all would be "ideal" and would avoid such depletion and attendant"crash" incidence. But, for the present, workers insist that some sortof lube is needed to reduce interface friction.

Thus, some lube is believed necessary--e.g., to prevent a slider fromprematurely "gouging" or otherwise marring or digging-into the discsurface, and soon "crashing". Conventional sliders (e.g., 3680 MemorexDD) conventionally operated (50 Åfilm of lube) are expected to have auseful life of about 10,000 stop-start cycles (cf. a contact start-stoptest is widely accepted as a measure of media integrity). "Low-lube"conditions reduce this to the order of a mere 1,000 cycles;(unacceptable in the industry). Workers theorize that a "crash" is oftenpresaged when disk-coating material is transferred onto a slidersurface--commonly because too much heat is developed by rubbing of theslider against the disc coating (such overheating evidentlybreaking-down the coating binder constituent and allowing the slider topick-up disc coating matter).

Workers would like to reduce lube thickness (well below the mentioned50-70 Å). But such "low-lube" conditions are not yet acceptable. Theyare viewed as attenuating the useful operating life of a disc-slidercombination. For instance, we have seen lube applied in the 20-60 Årange limit operating life to about 1,000 start-stop test cycles,whereas an "acceptable" operating life to workers corresponds to about5,000-10,000 cycles or more [Note: one start-stop cycle will beunderstood as initiated when a slider at rest is made to speed up andtake off to over-fly the disc and then land thereon to be returned torest].

It is a further object of this invention to ameliorate thesedifficulties and allow workers to not only overcome stiction and relatedproblems with conventional lube levels but to do so under "low lube"conditions and under conditions allowing sliders to fly ever closer tothe magnetic disc surface and still survive 10K contact start-stopcycles. This is proposed by providing the mentioned boss means on theslider.

In thinking of ways to relieve the mentioned "stiction" problems, anumber of approaches come to mind. For instance, one might considerchanging the traditional "circular" path of the slider about themagnetic disc to an elliptical path. This might reduce stiction effects(by imparting a centrifugal force to separate the slider from the disc),but such a solution seems difficult to implement and might presentundesirable side effects.

Or, one might curve the slider air-bearing surfaces (rail faces) toreduce plane-to-plane contact with the disc. However, such a curvedsurface is not easy to visualize and design and is problematic tomanufacture in quantity (consistent with yielding a slider that will flystably just a few micro-inches above a disc). Moreover, the resultingconverging/diverging air-flow paths could well make the slider unstable.

Or, one might apply a high frequency vibration to the slider disc-justbefore "start-time" to release the "stiction bond". This has been triedbut is not viewed as reliable.

Or, as revealed in the IBM TDB Volume 25, #9 Feb. 1983, one might heatthe disc lubricant to reduce its viscosity and thereby hope to reducestiction. However, this is somewhat impractical, e.g., since it requiresspecial heating means and related power and indicates problematicresidual thermal stresses in the slider suspension system [flexure, loadbeam, etc.].

Thus, the art is still awaiting a practical solution to "stiction" andrelated problems; a solution which is simpler to implement than theforegoing and which avoids their undesirable side effects. Our inventionprovides "anti-stiction bosses" as such a solution. For instance, ourtechnique is very simple to implement and brings no significant adverseside effects. In fact it has been somewhat surprising that such a simpleboss means could solve these problems and that such a protruding bosscould skid along the disc surface without injuring either itself or thedisc. It was also surprising to realize some other advantages using thisboss means, such as shorter, quicker "lift off" from the disc, relief ofexcessive stiction even under "heavy-lube" conditions, and allowing a"low-lube" disc to achieve satisfactory operating life.

"boss" in general

FIGS. 1'-4' schematically illustrate a magnetic recording slider SLconstructed and improved to include boss means according to principlesof this invention. The slider, and related means discussed herein, willgenerally be understood as constructed and operating as presently knownin the art, except where otherwise specified; the materials, methods,and devices and apparatus being implemented by known expedientsaccording to present good practice.

Thus, FIG. 1' depicts a conventional slider SL-1 resting on anassociated magnetic recording disc with a protruding "boss means", ormetal slug B, raising the forward end of the slider off the discsurface. As better seen in FIGS. 2', 3' and 4', slider SL-I will beunderstood as a relatively conventional three-rail "Winchester" slider,e.g., of the type used with a high speed disc drive, such as the Memorex3650. The slider is understood to carry thin film transducers tf (FIG.4') , mounted at, or adjacent, its trailing edge TE as known in the art.The three slider rails A₁, A₂, A₃ may be the order of 0.145 inch wideand include conventional ramp sections r₁, r₂, r₃, respectively,disposed forward of their leading edge portions. As workers know, thedisc-confronting faces of the rails define a prescribed "flight-plane"f--f (see FIG. 4'). Boss B will be understood as a tiny protrusion(e.g., relatively cylindrical or rectangular) projecting about 6micro-inches below this "flight-plane"--cf. below the leading portion ofthe middle rail A₂ (see FIG. 4'), preferably just aft of the associatedramp portion r₂.

Workers will recognize that so attaching a boss means "protuberance"relatively centrally off the forward portion of the slider will providea "bias pitch" when the slider is at rest [on the stationary disc]--andof course will drastically reduce the contact area between slider anddisc. [The slider faces are very, very smooth and flat--as is the disksurface and lube film thereon--and it is this interfacial contact ofsmooth flat surfaces that gives rise to "stiction"]. So providing aprotuberance will, in turn, reduce (and can all but eliminate) thepotential "stiction" force due to extreme flat conditions of theinterface (note that slider SL-I now rests only on the boss and itstrailing edge TE, rather than on the entire lengths of its slider railfaces).

The boss B will preferably protrude only-barely beyond the slider level(e.g., a few micro-inches-- preferably about 6u"--below flight planef--f in FIG. 4'); for instance, just enough to induce a fast efficientlift-off when the disc is suddenly rotated, yet not enough to interferewith air flow along the slider rails while they fly just above the disc.A protrusion of 5-10 micro-inches is found quite satisfactory under thesubject conditions as noted below in more detail [slider assuming to beflying about 24-35 micro-inches above the disc, which we assume wascovered with a lube thickness of about 20-60 Å. Here assume about 250Å=1 micro-inch]. A 6 micro-inch protrusion distance was settled-upon asa compromise between optimum head flying attitude (cf "bias") and astable rest configuration. And with excessive protrusion, the boss mighttend to shear-off on contacting the disc, whereas too little protrusion(e.g., 2 micro-inches or less) might not adequately relieve stiction orafford other advantages, such as "fast take off" (see below).

It seems preferable to-deposit such a miniscule metallic boss.Sputtering (e.g., SiC) is recommended here as a reliable, convenient wayto deposit a boss B with a protrusion of a few micro-inches (amicro-deposition). Particularly good results and a simple method havebeen realized by sputtering the subject boss B (FIGS. 1'-4') on themid-rail of slider SL-I just before mounting the slider on its supportflexure. To do this, one may readily mask-off all slider surfaces exceptat the boss site [as is well known in the art; photo resist might beused, as workers know]. Then, one can sputter the requisite "bossmaterial" (6 micro-inch) thickness relatively uniformly.

One preferred "boss material" with such a conventional slider [i.e., aslider made of Al₂ O₃ TIC material] is silicon carbide (SiC). However,workers will realize that other such (hard) boss materials compatiblewith good adhesion to such a slider might comprise titanium carbide(TiC), Al₂ O₃ or the like. [To make the boss of "slider material", orits mechanical equivalent, itself would, of course, be highly desirable,if such is convenient; e.g., this should yield optimal bonding,matching-thermal expansivity, etc.].

Somewhat surprisingly, alumina (Al₂ O₃) is a relatively non-preferredboss material since it is found relatively too soft when deposited inthe amorphous state [e.g., surviving for only 4-5K cycles in astop-start test]. And, while it is presumably quite a bit harder in thecrystalline state, the heating necessary to induce crystallinity (insitu) is believed potentially harmful to the transducer on the slider.

It appears preferable to deposit "boss material" that is somewhat of amatch in stoichiometry with the substrate slider material; elseadhesion, etc. may be inadequate. For instance, for a slider like SL-I,we found that a pure tungsten slug adhered very poorly to the[ceramo-metallic] slider; apparently no "pure metal" would give goodadhesion in such a case.

In any event, workers will appreciate that the "boss material" selectedfor deposition (or otherwise attached) will give sufficiently strongadhesion and hardness and other mechanical characteristics so as toremain in place and not significantly wear away during a full usefuloperating life [e.g., enduring at least 10K stop-start cycles, or a likedurability test]. The boss, as mentioned, will protrude below the sliderprofile only sufficient to substantially relieve "stiction" and relatedproblems, and very little more, lest its protruding profile disturbflight aerodynamics as it over-flies the disc [however, see below forthe piezoelectric alternative which may be "withdrawn" during flighttime, etc.].

RESULTS

The foregoing embodiment [FIGS. 1'-4'] was observed to give severalsurprising, highly desirable results.

More particularly, the so-improved slider [with protruding boss] wassubjected to "stop-start" tests giving surprising indications ofsuperior survivability (durability). (See data in FIG. 3'). A"stop-start test" involves placing a slider in operating relation with amagnetic recording disc and stopping and starting the disc repeatedly tocause the slider to "take off" and "land" under conditions simulatingactual use. The "survivability" of a slider-disc combination isadjudged. according to the number of such stop-start cycles that can berun before significant degradation occurs, especially a "crash" or othercatastrophic failure.

The subject embodiment [with the sputtered boss medially of the sliderrails] has been run through a stop-start test on a normally lubricateddisc [55 Å average applied depth of lube] in a high speed computer discdrive environment [Memorex 3680 disc drive]. Quite surprisingly, theprotruding "boss" neither wore away nor did any perceptible damage tothe disc surface over 10,000 cycles and beyond [and did not crash, as aconventional slider would likely have], while also evidencing arelatively lower "particle count" than with a "standard, non-bossed 3680slider".

Such results are summarized in FIG. 13' [note above that the slider heretook off and landed approximately 240 times per hour; that it was runconcentrically around a single disc track; and that 10,000 start-stopcycles corresponds to approximately 10 years of "normal operating use".A normal 3680 slider would have lasted for about 3,000 cycles, and thencrashed under these conditions].

This stop-start test (summarized in FIG. 13') is instructive. Note thatduring the first six to twelve hours a relatively high particle count[using a commercial grade particle counter--of 0.3-0.5 micron] wasexperienced--(cf. FIG. 13', e.g., peak at about 4 hours). This is rathernormal and is believed to result from a "burnishing" of the peaks andasperities on the disc by the slider as it skids over the disc surfaceduring take off and landing.

By way of illustration, one might also note that if a "crash" wereimminent during such tests, it would typically be preceded, and"flagged", by an enormous rise in particle count [e.g., an "explosion"of two to three times the running count in just a few seconds; then afew minutes later, a "groove" would appear, worn into the disc's testtrack (e.g., three to four minutes in usual case)--this quickly followedby a catastrophic "crash" [due, principally, to pick-up of disc materialby the slider]. Dotted-curve 13-A in FIG. 13' is intended to representsuch an "exploded" count and imminent crash.

Also, during this such a test, it was noted, quite unexpectedly, that aso-improved slider [with center boss protruding] appeared to "lift-off"relatively more quickly than normal. For instance, where a "standardunbossed 3680 slider" will lift-off and begin to fly when disc velocityreaches about 300 inches per second, the subject "bossed" embodimentlifted off at about 250 inches per second. This is possibly due to thefavorable "pre-bias", or tilt, created by the upstanding boss. Workersin the art will appreciate how valuable such an "early lift-off" is.This early lift-off is also believed responsible (at least partly) forthe marked decrease in initial particle count often observed with theinvention (e.g., see FIG.14', discussed below). This early lift-off willalso be desirable to more quickly bring the slider into a smooth,laminar-flow flight mode, reducing turbulence and noise during lift-offand generally affording better air bearing performance [allowing one toshorten the take off zones and thus increase available bit space on thedisc and increase disc life]. At any rate, workers will highly value aslider allowing earlier lift-off (at lower disc rpm).

This embodiment was also surprisingly superior under "low lube" ("thinlube") conditions, e.g., surviving 10,000 start-stops on a "depleted"lube thickness [about 20 Å applied], while generating relatively lessthan the normal number of "particles" ("macro-particles" about a certainsize; see FIG. 15' discussed below). Workers will appreciate howsurprising such results are; e.g., where a normal slider is uselessunder such "depleted lube" conditions since it will typically crash atless than about 1,000 stop-start cycles, a mere "bossing" of the slidercan give a normal operating life (10K+ cycles).

Workers will appreciate how very significant such a "thin lubecapability" is; and indeed how surprising it is that a slider with aprotruding boss would need less lubrication--not more! Conventionalthinking would have supposed that the boss would be more likely todig-into the disc, even with "normal" lube thicknesses--indeed weexamined the disc during start-stop testing, half-expecting to see a"groove" appear--yet none did! This was confirmed in a "Park Test",subjecting a "bossed-slider" to a normal 15 gm load as "parked" at reston a normal 3680 disc for 48 hours or more. No change or specialperceptible damage to the disc was apparent [that is, the disc was in nodifferent condition than with a normal slider].

This embodiment was also tested on an abnormally heavily lubricated disc[300-1,000 Å, well above the usual lube thickness]; and for aconsiderable and surprising number of cycles (5,000) the bossed sliderdidn't appear to stick to the disc at all. This is in marked contrast tothe performance of a "standard 3680 slider" which, under such heavylube, shows visible stiction at once, accompanied by a "pinging" noiseas the slider-support structure gets released from the disc.

Surprisingly, the only adverse effect of using such boss means seems tobe that a bit of "debris" can be generated--evidently by boss-disccontact during rest times--but the amount and particle size are notsignificant.

Workers can appreciate the foregoing results are quite unexpected and agreat surprise, really--especially since workers expected that (orwondered if) the protruding boss would dig into and damage the delicatedisc surface (e.g., more than the smooth slider rails normally do). Itwas apparent that it did not--on the contrary, the "bossed" sliderevidently does less damage, not more, to a disc surface.

In sum, workers will appreciate how surprising such results are using aboss-modified slider; how surprising that it performs better (longer)than a normal slider, whether on a normally-lubricated disc, on alightly-lubricated disc, or on a heavily-lubricated disc [e.g., earlierlift-off], and how surprising that it lasts enormously longer than anormal slider in "thin lube" conditions. Workers will especiallyappreciate the prospects for using such "bossed sliders" under "lowlube" (or even "no lube") conditions, especially where flying heightsare abnormally low (e.g., below about 10 micro-inches).

Workers will note that the foregoing not only teaches one how tomanufacture an improved slider, but also how to "retrofit" existingsliders [as do other embodiments below]. Workers will recognize thatsuch a "boss means" can readily be affixed on a conventional three-railslider [two-rail sliders would be similar]. Or, the sliders may bemanufactured exactly as presently, except that the manufacturer, or athird party, may simply add-on the desired boss means in the indicatedmanner. This is, of course, an option that makes the invention verypractical since one needn't radically upset the normal manufacturingmode, or radically change the vendor specs. of such sliders. Of course,the invention is also easy to incorporate into a slider manufacturingprocess.

FIGS. 1A', 1B' show a slider SL-II, replicating the slider of FIGS.1'-4' [e.g., with the same or like slider] with a similar boss B'deposited along the middle slider rail A'₂ just aft of its associatedramp r₂ ', except that, after completion, the middle rail A₃ ' isetched-away somewhat (as indicated along plane R-g in FIG. 1B') toessentially remove it as an air bearing surface. One might wonder what,if any, effect this has on slider performance (e.g., aerodynamics,etc.). Happily (and somewhat unexpectedly) we have found that there areno adverse effects at all.

In particular, slider performance during stop-start testing is superior(like that of the embodiment of FIGS. 1'-4'). For example, we testedthis bossed slider design SL-II in start-stop tests like thosementioned. One such is summarized in the plot of FIG. 14' [conditionsand presumptions the same as those mentioned for FIG. 13' above, etc.]with the so-improved slider being run over a normally lubricated [55 Åaverage depth] disc of the type used in Memorex 3680 disc drives.

Here, it will be seen that about 42 hours of stop-start testing wasquite successfully survived [no crash, etc.], with an unusually-lowparticle count being experienced throughout this period. [Note: A "low"particle count generally corresponds to less contact at the slider-discinterface]. From this, one might infer that one may cut-away, orotherwise eliminate, the center rail on a three-rail slider [althoughone need not do so!] and mount a protruding "boss means" thereon,according to the invention, and still derive the same sort of superior,surprising improvements as found with the preceding embodiment (cf .FIGS. 1'-4').

A like stop-start test was also performed on this "second embodiment"under "depleted lube" conditions [about 20 Å average lube depth]--withcomparably-long, successful results [about 36 hours without crash,etc.]. This test is represented in FIG. 15' [otherwise derived the sameas FIG. 14']. Of course, the "absolute" particle count here (FIG. 15')is considerably higher, as might be expected from the reduction in lubethickness and increased friction. However, this is still acceptable (is"clean enough") and should not lead to "crash" or other failure.

Slider SL-III in FIG. 5' represents another embodiment; essentially thesame as SL-I in FIGS. 1'-4', except that three bosses, rather than one,are applied [each on a respective rail, just aft of a respective sliderramp, as with boss B SL-I] all being identical in size and constructionof course. This embodiment will perform essentially like SL-I exceptthat, with the added boss means at the front, a "higher pitch" sliderresults--something that is desired in certain instances.

The embodiment of FIG. 5' (SL-III) is essentially replicated for atwo-rail slider SL-IV as seen in FIG. 6', with each (identical) bossprotruding about 6 micro-inches (beyond "flight-plane") and beingdeposited on a respective rail (each rail about 0.0167 inch wide), justaft of its respective ramp as before.

Here, the results were essentially as in the first embodiment SL-I.

In a two-rail slider (e.g., like that of FIG. 6') SL-V, a singleelongate boss means, or slug B-V, is here deposited midway between therails and just aft of the ramp zone. This slug B-V is thus deposited onthe medial ("throat") surface B_(s) between the rails, preferably beingdeposited in the fashion of those in the foregoing embodiments.

Here, the results were generally as with the embodiment of FIGS. 1'-4'.

The two-rail embodiment of FIG. 6' is replicated in FIG. 12' as modifiedslider SL-VI, except that, here, instead of the (2) bosses beingdeposited, they are "cold worked", or shaped during lapping, into anappropriate "boss site" portion of the slider rails, as workers in theart will understand. For instance, well-known techniques are feasiblehere--e.g., as a "roughening process", understood as raising "bumps"(micro-roughening) on the order of about 6 micro-inches above the normalslider surface.

For instance, one may readily gouge-up protrusions on the order of 50 Åabove such a (slider) surface, as workers know. Such protrusions can besurprisingly effective as "multiple boss means", and appear to presentno adverse side-effects (even during the brief contact with the discduring landing).

Here, the results achieved will be the same as for FIG. 6'.

In FIGS. 9'-11', another alternate embodiment SL-VII is produced byessentially replicating embodiment SL-V of FIGS. 7' and 8', butreplacing slug B-V with a "piezo-slug" P_(Z) of relatively foreshortenedheight, i.e., P_(Z) is just tall enough, or almost so, to intercept the"flight-plane" A--A of the slider rail faces (air bearing surfacesABS--like plane f--f of FIG. 4'), yet not quite enough to projecttherebeyond--being about 0-6 micro-inches. However, once energized asunderstood by workers (means understood, but not shown or specifiedhere), element P_(Z) will "self-elongate" enough to intercept and crossthe flight-plane A--A (e.g., extend 6 micro-inches or so beyond A--A;see dotted line representation of the elongation of P_(Z) in FIGS. 9'and 11'). Thus, boss P_(Z) will be selectively thrust out to protrudelike the preceding boss means, and to yield the same "protruding boss"effects during a selected "boss mode" (as with the prior embodiments,but doing so only selectively, and only when energized, as known bythose skilled in the art--i.e., functioning as a "selectively-protrudedboss means").

More particularly, this technique will entail embedding a smallpiezo-element P_(Z) at the center of the slider, between the twoco-planar air bearing surfaces [rail faces ABS] and providing selectiveenergizing piezo-power therefor. Thus, under "Rest" (no-power)conditions, the ABS and the piezo-surface will be in roughly the sameplane [possibly have been lapped together; or the piezo may be slightly"foreshortened", as mentioned above].

But, in the "energized" state, the piezo-element will elongate toprotrude (a few micro-inches) beyond the ABS plane A--A. This will alsointroduce a "bias pitch", as before; preferably on the order of a fewhundred micro-radians. Therefore, only a very small portion of theintegral slider body (trailing-edge plus P_(Z)) will be in contact withthe disc at "Rest", or when sliding contact is made during landing ortake off.

As with the "fixed (non-piezo) protruding boss means" embodimentspreviously discussed, this protruding piezo-boss may be expected toradically reduce slider-disc contact as to alleviate, if not entirelyeliminate, problematic stiction forces acting between the ABS surfacesand the disc lubricant. Just before the start of disc rotation,energizing power to the piezo element P_(Z) may be turned-off,contracting the piezo-element to its non-protruding length.

A "bias pitch" of various selectable degrees can be provided when thedisc is stationary merely by appropriately energizing the piezo-boss("piezo-slug") to induce a desired associated elongation. And, theelement may be energized before the disc comes to rest (that is, duringlanding) so that there will be sliding contact only between P_(Z) andthe slider's trailing edge. Then, if the piezo P_(Z) is elongated beforethe disc stops, it can help reduce excess contact force (evidentlyincreased hydrodynamic pressure under the piezo-boss "cushions" of theslider).

Such incorporation of a "piezo-boss" element, appropriately energizedand located, is a simple technique to implement. The piezo element,being a tiny capacitance device, will consume negligible power (e.g.,the voltage necessary for such operation should be in the range of 20-35volts for an elongation of the order of a few micro-inches).

RESULTS

This embodiment, in principle, yields results like the embodiment ofFIG. 7', with the added advantage that debris-generation is much lesslikely.

Workers who prize such advantages may deem it worth the extra expenseand trouble to use the piezo form of the invention.

In a different, but related, embodiment, one may use a boss like B inSL-I or the like and provide heating means to heat the boss enough toelongate it as required [as with the piezo-boss] from a condition ofcoincidence with the slider plane to about 5-10 micro-inches therebeyond[e.g., one can do this with an embedded coil and selectively applyingcurrent]. Whatever boss pattern (type) is used, it may usually belocated anywhere on the slider face, unless a "forward pitch" isdesired.

Workers may also contemplate alternative ways of depositing such a bosssuch as by plating, or vapor depositing and etching - back, or vacuumdeposition, flame coating, ion-gun deposition (local) oxidation, etc.,as known in the art.

Now, workers might, at first blush, think that a plastic boss would bepreferable, e.g., a teflon (tetrafluoroethylene) boss that has arelatively low coefficient of friction. Surprisingly, this doesn'tappear to be necessary or important--although one might deposit aplastic (like teflon) by providing a suitable "adhesion-site" [e.g.,epoxy bond a teflon substrate in place of the above bosses andthereafter cold working, or depositing a super-layer of teflonthereon--e.g., by vacuum evaporating teflon stock so it depositspreferentially onto this "teflon substrate"]. As some workers may know,it is, unfortunately, not possible to lap, or otherwise preciselymachine, plastic to within a few micro-inches as required for thesubject invention.

In summary, it is preferred that one, or more, fixed or extendable bossmeans (micro-protuberances) be provided, front and center of a slider,or else symmetrically about the forward slider end, to function asanti-stiction means, bias means and the like.

"boss" combined with "back-bar"; most preferred

We have found that one may advantageously add "back-bar means" tosliders equipped with such "boss means", with little or no perceptibletrade-off. The following most preferred Example A illustrates this.

Ex. A: Slider with boss and back-bar (FIGS. 24A, 24B):

Slider 111 in FIGS. 24A, 24B (after FIGS. 19A, 19B, with boss ms added,e.g., as per FIG. 1A', etc.) will be understood as a "self-loading"slider provided with back bar means (cf. back-bar BB; and associatedpurge channel 151) and in every respect like the slider of FIGS. 19A,19B, except that a medial boss means "ms" is also provided on the flyingsurface thereof (centrally, just aft of ramps, e.g., as in FIG. 1A',etc.).

Workers will find that such a boss ms (or equivalent boss means) willprovide the usual "boss advantages", noted above (e.g., relieve"stiction"), yet without interfering perceptibly with "back-bar"operation (e.g., as noted above) or with other slider characteristics(e.g., slider 111 can still be "self-loaded" and "self-unloaded" asknown in the art).

Moreover, there are special advantages to using "boss means" with aback-bar equipped slider. For instance, when such a slider is operatedon a "lubed" disc surface, the miniscule back-bar cavity (e.g., only 150u" deep or so, and other such micro-cavities, e.g., as in a self-loadingslider) is all too apt to take up, and secrete, impurities such as lubefluid, atmospheric smoke and other gases which can increase "stiction".Thus, anti-stiction boss means is all the more called for.

Also, a boss is co-advantageous with back-bar means; both accommodatefine-polishing, etc. of the slider's flying surface without concern overdamaging it, or damaging the slider's "tail" or delicate means thereon(e.g., a fine Al₂ O₃ film there, or end-mounted transducers or like"chips")--e.g., especially because the "tail", etc. is isolated from therest of the flying surface by its channel or "moat" (e.g., see channel151 in FIGS. 24A, 24B), and because a boss can be "raised" late in themanufacturing stages (e.g., by cold-working or micro-roughening thesurface as for the embodiment of FIG. 12'). Both the back-bar and theboss can better accommodate otherwise problematic finishing operations,such as heat-polishing (e.g., with a laser). And a back-bar equippedslider is apt to be particularly susceptible to stiction (e.g., whereslider-disc contact area reduced; where slider's contact surface isparticularly smooth and/or lube-filled)--and thus is an especially aptsubject for our anti-stiction boss means.

And, surprisingly, workers will find that most such "back-bar-equipped"sliders are still relatively insensitive (less sensitive), duringoperation, to changes in loading force and/or disc speed (rpm); whilestill accommodating automatic low-speed unloading (for "self-unloading"sliders).

It will also be somewhat surprising that, even where a boss is used, theslider's aerodynamic characteristics are kept intact and back-barproperties unimpaired. For instance, the back-bar means (e.g., as inFIGS. 24A, 24B) can still be used to fine-burnish a disc surface,polishing-down micro-asperities thereon. Such may be done during a "testrun" of the "slider-with-back-bar" over the disc recording surface,preferably at relatively high speed (note a back-bar accommodatesparticularly small flying-heights). This can allow workers to dispensewith the special "burnishing head" commonly used for this purpose,saving the special fabrication steps associated therewith.

Some effects of such "burnishing" are illustrated (plotted) in FIGS.25A, 25B. In FIG. 25A a given disk recording area (cf. radius 4.0"-6.9")will be understood as exhibiting an unburnished surface roughness as perthe indicated plot [cf. RMS voltage output of acoustic emission sensorwith disk rotated at 1800 rpm; voltage spikes corresponding to majorasperities]. The same disk surface, after burnishing with such a backbar-equipped-slider, is indicated in FIG. 25B, tested the same way [noteall major asperities removed by such burnishing, and many minor ones].

Variations:

And workers will recognize that a slider equipped with any such back-barmeans can be advantageously provided with other boss means to yield likeresults.

It will be understood that the preferred embodiments described hereinare only exemplary, and that the invention is capable of manymodifications and variations in construction, arrangement and usewithout departing from the spirit of the invention.

Workers will appreciate that such back-bar/purge channel features aremost apt for use with negative pressure-type sliders which fly at lessthan 10 u". Workers will also appreciate that, in appropriate instances,one may alternatively use such design back-bar/purge channel with lowflying, positive pressure (Winchester) sliders.

Further modifications of the invention are also possible. For example,the means and methods disclosed herein are also applicable to other discmemory systems (e.g., plated media, floppy discs) as well as to flexiblemedia in general. Also, the present invention is applicable forproviding such purging, etc., with other forms of low-mass recordingand/or reproducing systems, such as those in which data is recorded andreproduced optically. Also, the present invention is applicable forproviding "-anti-stiction" boss means (or boss-bias means) to reducerelated forces between any such smooth surfaces, especially to reducerelative friction therebetween, whether the surfaces are lubricated ornot.

The above examples of possible variations of the present invention aremerely illustrative. Accordingly, the present invention is to beconsidered as including all possible modifications and variations comingwithin the scope of the invention as defined by the appended claims.

What is claimed is:
 1. A method of adapting a magnetic recording sliderhaving a prescribed shallow "flying cavity" on its media-confrontingface to exhibit "self-purging", better stability and increasedstiffness, and to resist "stiction", this method including: providingback bar means disposed across the cavity on the trailing face of theslider, while adapting this back bar means to include purge channelmeans disposed in fluid communication between the cavity and the ambientatmosphere whereby to better purge the cavity of gas and associatedcontaminants; and also providing "boss means" on the forward portion ofthis face, such as to pitch-up this face, at least sufficient to relievestiction, wherein the boss means comprises one or moremicro-protuberances projecting a prescribed micro-dimension below theflying-surface of this face, but insufficient to interfere with sliderflight.
 2. The method as recited in claim 1, wherein the boss means isalso adapted to accommodate reduced flying height.
 3. The method asrecited in claim 1, wherein the boss means is also adapted toaccommodate reduced lube thickness along with extended operating life.4. The method as recited in claim 1, wherein the boss means is adaptedto accommodate shorter take-off distances and faster lift-off.
 5. Themethod as recited in claim 1, wherein the cavity functions as a"negative pressure passage" and said urge channel means is arranged andconstructed to communicate with the exit end of this "passage" andquickly empty it and purge it of debris.
 6. The method as recited inclaim 5, wherein the purge channel is formed to comprise a groove cutinto the trailing portion of the flying face of the slider and extendstransverse the flying direction.
 7. The method as recited in claim 5,wherein the cavity is the order of one to a few hundred u" deep andseveral dozen mils wide and the purge channel is formed to beconsiderably larger, up to a few mils deep; and the boss means projectsa few micro-inches or less.
 8. The method as recited in claim 7, whereinthe slider is the "self-loading type" adapted to fly at a minimum heightof one to several u", the back bar means being thus constructed andarranged to render the slider more stable despite moderate changes inloading; and the boss is also adapted to produce a slider that generatesfewer "macro-particles" and gives a lower "particle count".
 9. Thecombination as recited in claim 1, wherein the boss means is alsoadapted to give a prescribed "bias pitch" to the slider, while alsoavoiding "yaw" of the slider face relative to the media surfaces. 10.The combination as recited in claim 1, wherein the boss materialcomprises "slider material" or the mechanical equivalent thereof, atleast on the exposed face thereof.
 11. The combination as recited inclaim 10, wherein the slider face is comprised of a carbide of siliconor titanium, or of alumina, and the face of the boss means comprises acarbide of silicon or titanium.
 12. The combination as recited in claim1, wherein the boss means is arranged to project only very slightlybeyond the flight-surface of the slider means, just enough to counteractstiction forces, yet insufficient to upset flight characteristics. 13.The combination as recited in claim 1, wherein the boss projection isthe order of a few micro-inches or less.
 14. The combination as recitedin claim 12, wherein the boss projects about 5-10 u" for a flight-heightthe order of 24-30 u".
 15. The combination as recited in claim 1,wherein the boss means are retrofitted on a complete, existingpre-manufactured slider.
 16. The combination as recited in claim 1,wherein the boss means comprises a piezo-electric slug disposed mediallyon the forward portion of the slider face and just tall enough, oralmost so, to intercept the slider "flight plane" defined by associatedslider rail faces; and is also arranged to be selectively activateableat prescribed "projection-times" to be sufficiently elongated to crossthis "flight plane" and extend therebeyond.
 17. The combination asrecited in claim 16, wherein associated piezo-power means is arranged toautomatically so activate the piezo-slug at said "projection-times". 18.The combination as recited in claim 17, wherein the piezo-slug isadapted to extend up to a few micro-inches beyond the "flight plane".19. The combination as recited in claim 17, wherein the piezo-slug is toactivated and so elongated during periods of "high stiction".
 20. Thecombination as recited in claim 19, wherein the piezo-slug is soactivated and so elongated when the slider is "landing" or "taking-off"or "at rest" on an associated disk.
 21. The combination as recited inclaim 16, wherein the piezo-slug is so activateable to also be projectedfrom the slider face sufficient to give the slider means a prescribed"pitch bias" when at rest on an associated disk surface.
 22. A method ofproviding magnetic recording slider means including the stepsof:providing a prescribed anti-stiction boss means on a forward portionof the record-confronting face thereof, and providing back-bar meansalong the railing edge of this face.
 23. The method as recited in claim22, wherein the boas means is arranged and adapted to be selectivelyprojected beyond this face during "stiction"-prone periods.
 24. Thecombination as recited in claim 23, wherein the boss means comprises aslug means adapted to be selectively energized sufficient to elongateand be projected a prescribed protruding distance beyond the flightplane of the slider means; and wherein activation means is also arrangedto so elongate the slug means automatically at prescribed projectiontimes.
 25. Improved magnetic recording slider means having prescribedanti-stiction boss means on a forward portion of the record-confrontingface thereof, plus back bar means along the trailing edge of this face.26. The combination as recited in claim 25, wherein the slider has aprescribed shallow "flying cavity" on its media-confronting faceprojecting a prescribed micro-dimension beyond the flying-surface of theface, insufficient to interfere with slider flight; and wherein thisback bar means includes purge channel means disposed in fluidcommunication between the cavity and the ambient atmosphere whereby tobetter purge the cavity of gas and associated contaminants.
 27. Thecombination as recited in claim 26, wherein the boss means is alsoadapted to accommodate reduced flying height.
 28. The combination asrecited in claim 26, wherein the boss means is also adapted toaccommodate reduced lube thickness along with extended operating life.29. The combination as recited in claim 28, wherein the boss is alsoadapted to produce a slider that generates fewer "macro-particles" andgives a lower "particle count"; and wherein a plurality of R/Wtransducer means are mounted along the back bar means.
 30. Thecombination as recited in claim 28, wherein the boss means is adapted toaccommodate over 10,000 stop/start cycles.
 31. The combination asrecited in claim 26, wherein the boss means is adapted to accommodateshorter take-off distances and faster lift-off.
 32. The slider asrecited in claim 26, wherein a plurality of R/W transducer means aremounted along the back bar means.
 33. The slider as recited in claim 32,wherein the back bar means is constructed and arranged to include a barmember extending fully across the cavity exit zone and across the sliderwidth.
 34. The slider as recited in claim 33, wherein the purge channelmeans is formed to comprise a prescribed shallow groove between said barmember and the exit zone of the cavity, this groove communicating withthe sides of the slider and extending relatively transverse said flyingdirection.
 35. The slider as recited in claim 34, wherein the slider isa "self-loading" type.
 36. The combination as recited in claim 25,wherein the boss means is also adapted to give a prescribed "bias pitch"to the slider, while also avoiding "yaw" of the slider face relative tothe media surfaces.
 37. The combination as recited in claim 25, whereinthe slider face exhibits two or three rail means and the boss means isdisposed on the forward portion of one or several rail means and/or isdisposed therebetween; wherein the slider includes a shallow flyingcavity on this face and wherein the back bar means is constructed andarranged to include a bar member extending fully across the cavity exitzone and across the slider width.
 38. The combination as recited inclaim 37, wherein the slider face is characterized by two rail means andthe boss means is disposed therebetween at the forward portion.
 39. Thecombination as recited in claim 37, wherein the slider face ischaracterized by three rail means, wherein the mid-rail means iscut-back at least at its forward portion and replaced by a boss meansthere.
 40. The combination as recited in claim 39, wherein the mid-railmeans is cut-away completely and a boss means disposed o the forwardportion on the site thereof.
 41. The combination as recited in claim 25,wherein the boss material comprises "slider material" or the mechanicalequivalent thereof, on the forward portion of the exposed face thereof.42. The combination as recited in claim 41, wherein the slider face iscomprised of a carbide of silicon or titanium, or of alumina, and theface of the boss means comprises a carbide of silicon or titanium. 43.The combination as recited in claim 25 as characterized by piezo-bossmeans arranged and activateable to be selectively projected only veryslightly beyond the flight-surface of the slider means, just enough tocounteract stiction forces, yet insufficient to upset flightcharacteristics.
 44. The combination as recited in claim 43, whereinthis projection is the order of a few micro-inches or less.
 45. Thecombination as recited in claim 44, wherein this projection is about5-10 u" for a flight-height the order of 24-30 u".
 46. The combinationas recited in claim 25, wherein the boss means is retrofitted on acomplete, existing pre-manufacture slider, and wherein the sliderincludes a shallow flying cavity on its face, and wherein the back barmeans is constructed and arranged to include a bar member extendingfully across the cavity exit zone and across the slider width. 47.Improved magnetic recording slider means having prescribed anti-stictionboas means on a forward portion of the record-confronting face thereofadapted to be selectively projected therebeyond; plus back bar means onthe trailing end thereof.
 48. A method of adapting a magnetic recordingslider having a prescribed shallow "flying cavity" on itsmedia-confronting face to exhibit "self-purging", pitch-up, betterstability and increased stiffness, this method including:providing backbar means across the cavity on the trailing face of the slider, whilealso adapting this back bar means to include purge channel meansdisposed in fluid communication between the cavity and the ambientatmosphere whereby to better purge the cavity of gas and associatedcontaminants; while also providing boss means on the forward portion ofsaid face, sufficient to induce enough pitch-up to alleviate stiction.49. The method of claim 43, wherein the disk confronting slider faceportions for defining a prescribed flight-plane in its movingtransducing mode, with anti-stiction boss means disposed on each saiddisk-confronting portion face so as to project toward a subject disk,said boss means being adapted for spacing said face from a subject diskand comprising:disposing slug means medially on forward portions, only,of at least some slider face portions, and making said slug meansproject sufficiently to cross this "flight plane" and barely extendtherebeyond, and to thereby reduce "stiction", and pitch-up the slidermeans when the said slider is "landing", or is "taking-off" or is "atrest" on the associated disk.
 50. The method of claim 49, wherein saidslug means so projects up to twenty micro-inches beyond said flightplane.
 51. Magnetic disk recording slider means for presentingtransducer means, said slider means having anti-stiction boss means onone or more disk-confronting face portions thereof; said boss meansbeing adapted for spacing said face from a subject disk and projectingtoward a subject disk, and being disposed medially on leading portionsof at least some disk-confronting face portions to project awaytherefrom, at least sufficient to give said carrier means a prescribed"pitch-up bias" when at rest on the associated disk surface; with alltrailing portions free of said boss means; and cavity means along saidface, being closed at its trailing portion by purge channel means. 52.The magnetic disk recording slider means of claim 51 wherein said bossmeans so projects twenty micro-inches or less.
 53. The magnetic diskrecording slider means of claim 51 wherein said face defines an airbearing surface and wherein said boss means is projected only veryslightly beyond said air-bearing-surface, just enough to counteractstiction forces, yet insufficient to seriously upset flightcharacteristics.
 54. The magnetic disk recording slider of claim 53wherein said boss means comprises one or more like slugs projecting veryslightly beyond the plane of the said air-bearing surface, sufficient torelieve stiction, yet insufficient to interfere with flight.
 55. Themagnetic disk recording slider means of claim 51 wherein said faceincludes a pair of disk-contacting rail means for affording combinedcontact/air-bearing surfaces; and wherein said anti-stiction boss meansis disposed centrally, between said disk-contacting rail means, withface areas aft thereof being entirely smooth.
 56. The magnetic diskrecording slider means of claim 51 wherein said boss means has a heightonly just sufficient to relieve stiction.
 57. Magnetic recording slidermeans for presenting transducer means, said slider means having at leastone disk-confronting face for resting upon, and interacting with, thelubricated surface of a magnetic recording disk, said slider meansincluding:one or more boss means disposed only on forward portions ofeach said record-confronting face and projecting toward a subjectmagnetic recording disk sufficient to alleviate stiction and relatedproblems; said boss means being adapted for spacing said face from asubject disk, plus cavity means along said face, being closed at itstrailing portion by purge channel means and by back bar means. 58.Improved magnetic recording slider means for presenting transducermeans, said slider means having a disk-confronting face defining theslider flight-plane, and having anti-stiction slug means on each saidrecord-confronting face, said slug means being adapted for spacing saidface from a subject disk and being disposed medially and only on forwardportions of each said record-confronting face and having sufficientheight to extend slightly beyond said "flight-plane"; plus cavity meansalong said face, being closed at its trailing portion by purge channelmeans and by back bar means.
 59. The magnetic disk recording slidermeans of claim 58 wherein said slug means extends up to twentymicro-inches beyond the said flight plane.
 60. Magnetic recording slidermeans for presenting transducer means, said slider means having at leastone disk-confronting face better adapted to rest upon, and interactwith, the lubricated surface of a magnetic recording disk, said slidermeans comprising:one or more like boss means disposed only on forwardportions of each said record-confronting face, and projected toward asubject magnetic recording disk, sufficient to improve the "rest"condition of each said slider face on the lubricated surface of saiddisk; said boss means being adapted for spacing said face from a subjectdisk; plus cavity means along said face, being closed at its trailingportion by purge channel means.
 61. Improved magnetic recording slidermeans for presenting transducer means, said slider means having at leastone disk-confronting face defining the slider flight-plane, and havinganti-stiction slug means on each said record-confronting face, said slugmeans being adapted for spacing said face from a subject disk and beingdisposed only on forward portions of each said slider face and having aheight which extends only slightly beyond said "flight plane"; pluscavity means along said face, being closed at its trailing portion bypurge channel means and by back bar means.
 62. The magnetic recordingslider means of claim 61 wherein said slug means is so extendedsufficient to relieve "high stiction" conditions.
 63. The magneticrecording slider means of claim 51 wherein said slug means is soextended sufficient to improve the interaction of said disk-confrontingface with the media surface when the said magnetic recording slidermeans is "landing" or is "taking-off or is "at rest" on an associateddisk.
 64. The magnetic recording slider means of claim 61 wherein saidslug means is so extends up to a few micro-inches beyond the said flightplane.
 65. Magnetic disk recording slider means for presentingtransducer means, said slider means having anti-stiction boss means on adisk-confronting face defining an air bearing surface and including apair of disk-contacting rail means thereof; said boss means beingadapted to spacing said face from a subject disk and projecting toward asubject disk, only very slightly beyond said air-bearing surface, justenough to counteract stiction forces, yet insufficient to seriouslyupset flight characteristics; and being disposed medially on the forwardportion of said disk-confronting face to project away from said face, atleast sufficient to give said carrier means a prescribed "pitch bias"when at rest on the associated disk surface; said boss means thus beingdisposed centrally, between said disk-contacting rail means, with faceareas aft thereof being entirely smooth; plus cavity means along saidface, being closed at its trailing portion by purge channel means.
 66. Amethod of stabilizing a magnetic recording slider having a prescribedsingle shallow "flying cavity" on its media-confronting face, thismethod comprising:providing back bar means so as to terminate saidcavity; and disposing associated transducer means across the trailingface of the slider; while arranging this back bar means to include purgechannel means cut into said trailing face to be in fluid communicationbetween the cavity and the ambient atmosphere and being sufficientlylarge to better purge the cavity of gas and associated contaminants, andto isolate said trailing face and transducer means mounted there, fromexit-flow and its associated turbulence and debris; while also providingboss means on the forward portions of said face, sufficient to alleviatestiction.
 67. A method of stabilizing a magnetic recording slider havinga prescribed single shallow "flying cavity" with a medial air bearingsurface on its media-confronting face, this method comprising:providingback bar means and disposing it across the trailing face of the sliderto terminate said medial air bearing surface, and to thus be adapted toblock air flow along said cavity, while presenting a full-width trailingedge for mounting transducer means; cutting transverse purge channelmeans deeply into said air bearing surface so as to be in fluidcommunication between the cavity and the ambient atmosphere whereby tobetter purge the cavity of gas and associated contaminants; this backbar means and purge channel means thus being arranged to coact inisolating said transducer means from the flow or exit-air from saidcavity and from associated turbulence and debris; while also providingboss means on one or more leading portions of said air bearing surface,sufficient to relieve stiction.